Utilising Flyash Paste Backfill

Underground » Environment - Subsidence and Mine Water

Published: August 01Project Number: C7033

Get ReportAuthor: Mike Gowan | Golder Associates

Society is in transition to a policy of sustainability - a long term approach that emphasises the efficient use of resources. To continue in business and minimise the negative commercial impacts of Government policies and taxes, industry has to engage its stakeholders and develop technologies which deliver sustainability.

Three areas of response to negative community concerns include:

  • Greenhouse gas mitigation;
  • Environmental research to provide the supporting science in new and existing projects; and
  • R&D to respond to negative community sentiments that can, and do, threaten access to coal reserves.

The research and demonstration of waste minimisation of power station fly ash carried out for this ACARP project has provided a significant breakthrough for the coal sector. Apart from technology issues, mining environmental and community issues can be addressed by this project.

Coal reserves in the Newcastle area are being sterilised due to the risks associated with post mining surface settlements. Selective backfill using paste fly ash, has the potential to increase the reserves accessible to mining by providing an economic and environmentally acceptable backfill material. However, there has been no large scale economically feasible use of paste backfill in coal mines anywhere in the world to date.

There is a unique opportunity in the Newcastle coal mining area to exploit the large quantities of fly ash available from the adjacent power stations to selectively backfill coal mines and open up large areas of previously sterilised coal reserves. While fly ash, combustion ashes and other mining wastes have been used for coal mine backfill, they have generally been limited in their application. Large volumes of fly ash have been used for backfill in South Africa, but like much of the other backfills, this has been as an hydraulic slurry, with large volumes of supernatant water associated with the settling of the materials.

Full tailings paste backfill is being used in hard rock mines, is proving to be a viable and economic alternative to other backfill methods. Paste backfill has the following advantages over an hydraulic backfill:

  • Paste is an environmental friendlier backfill - it exudes virtually no water on placing and as a result requires less water management;
  • Paste requires far less underground containment preparation than hydraulic backfill; and
  • Paste backfill placement operations do not have to be continuous - it has no critical flow velocity and can be left stationary in the distribution system for some time.

Testwork carried out for the Bayswater fly ash disposal system has shown that a high density fly ash slurry can be pumped a considerable distance. This study set out to confirm the suitability of fly ash to form paste mixtures and to demonstrate how they can be used as a successful backfill.

Backfills are being used overseas for a number of purposes, including thick seam, bord and pillar and longwall mining operations. This study proposes to demonstrate, through a number of critical stages, how this experience can be adapted to the Australian conditions with the use of fly ash as the backfill material. It is intended that this study will lead to the general application of backfill using a range of materials, potentially including coal washery rejects.


Health and safety, productivity and environment initiatives.

Recently Completed Projects

C27039True Triaxial Strength Of Coal Measure Rocks And Its Impact On Roadway Stability And Coal Burst Assessment

Rocks in the ground are subject to a range of stresses. The stresses...

C3063Underground Vehicle Design Standards And Statutory Implications

The Australian underground diesel vehicle fleet has evolved since di...

C3064Conveyor Belting And Lagging Shear Characteristics - Drive Drum Slip

The primary aim of this project was to investigate the relationsh...


Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C26029Geological Controls On Fluorine And Phosphorus In Bowen Basin Coals

Increasing global restrictions on fluorine in product coal prompted ...

C28033Raw Ash To Yield Relationships

Correct outcomes in yield predictions for product ash from coal bore...

C27038Establishing Self-Sustaining And Recognisable Ecological Mine Rehabilitation

In recent years an increasing interest has been placed on mining ope...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27064Dry Beneficiation Using FGX And X-Ray Sorters

Conventional dry processing methods engage a single beneficiation de...

C26010Multi-Sloped Screening Efficiency With Changing Strokes, Frequencies, Feed Solids And Feed Rates-Pilot Plant Study

Optimising multi-sloped screens is often described as an art and the...

C28059Impact Of Water Quality In Coal Handling And Preparations Plants

The objective of this project was to deliver a concise reference do...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement

This multi‐phase project is concerned with the mitigation of m...

C27054Optimisation Of A Thermal Flow Reversal Reactor For Ventilation Air Methane Mitigation

Ventilation air methane (VAM) generally accounts for 50-85% of the t...

C28076Selective Absorption Of Methane By Ionic Liquids (SAMIL) - Phase 2 Demonstration In A Packed Bed Reactor

An alternative approach to high temperature oxidation of ventilation...

Mine Site Greenhouse Gas Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community


National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook